In recent years, automatic identification procedures have become very popular in various fields. Some of the automatic identification procedures involve RFID systems. An RFID system typically uses RFID tags and a reader for the tags. An RFID tag (often referred to as a “transponder”) typically includes (i) an antenna which is electromagnetically coupled to a reader, and (ii) an IC (integrated circuit) chip which can store information for identification purposes. The reader typically includes an RF transmitter, an RF receiver, and an antenna to “interrogate” the RFID tags, and to remotely retrieve information stored in the RFID tags.
In some situations, the user of an RFID system may need a wider coverage in space to read information stored in RFID tags from a greater distance. One way to achieve this goal is to increase an RF power output by the reader to interrogate the tags, or to increase a gain of the reader antenna.
Alternatively, the user can use a repeater located between the reader and the RFID tags so that the repeater relays RF transmission from the reader to the RFID tags, and vice versa. Examples of such repeaters are found in Japanese Laid-open Patent Publication Tokukai 2004-94532, and Japanese Registered Utility Model 2528386.
In view of the above, it would be desirable to have improved repeaters which are capable of increasing a coverage area in space to interrogate RFID tags located more distant from an RFID reader.